


Genetically Modified Bloodlust

by Vaerien



Category: Assassination Classroom
Genre: Alternate Universe, Alternate Universe - Canon Divergence, Angst, Gen, more tags to be added as the story progresses
Language: English
Status: In-Progress
Published: 2016-09-03
Updated: 2016-10-30
Packaged: 2018-08-12 16:58:49
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 3,714
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7942126
Author URL: https://archiveofourown.org/users/Vaerien/pseuds/Vaerien
Summary: <blockquote class="userstuff">
              <p>A certain blue-haired boy gets a major (albeit faulty) upgrade in assassination techniques.</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> Hey there! Thought contributing to this fandom would be nice so here's my first AssClass fic. Feel free to leave criticism/suggestions :)  
> -  
> UPDATE (Oct 11): I'm alive! Schoolwork is consuming my life, though. Rest assured, this story will be continued ^-^

“Hey… thanks for coming here, Itona.” Nagisa said, taking a sip of his latte. “I really appreciate it; after all, you’re the only one in the class who knows about this stuff…” He gave off a little chuckle and blushed, desperately hoping that he wasn’t coming off as awkward.

The other boy didn’t respond. He was in a trance-like state, mindlessly staring into his drink with a blank look.  
  
“Itona?” Nagisa asked, anxious. He leaned forward to tap him on the shoulder. Before he could do so, Itona’s head snapped up, his eyes creating an unnerving gaze.

“Yeah. It’s no problem,” he said, before diverting his attention back to his coffee.

The pair were currently at Class 3-E’s favourite café: a small, cozy establishment located a good distance away from the rest of the school. Here, the class was free to chill without being disrupted by the rest of the Kunugigaoka tyrants.

Nagisa had invited Itona to the location for a little ‘lunch date’ to discuss rather important matters; matters that he didn’t feel comfortable taking to his other friends, or even Koro-Sensei.

“So,” Itona started, his voice cool. “What did you want to talk about, Nagisa?”

Nagisa considered for a moment, looking down at his half-eaten muffin. All of a sudden, the meeting didn’t seem like a good idea. Maybe he was overthinking things, or not placing enough faith in his own abilities. Maybe his assassination attempts wouldn’t benefit from what he was planning to do.

 _Whatever,_ he mused, looking back up at Itona’s curious gaze. _There’s no sense in backing down now._

“How did you get your tentacles?”  
  
“Oh?” Itona responded, staring at Nagisa in confusion. “I thought you and the rest of the class knew my backstory.”

Nagisa gulped and gave a nervous smile. _I should’ve known that he wouldn’t be quite open with the details,_ he thought, shakily taking a sip from his drink.  
  
“Yeah, but…” Nagisa replied, voice shaking. “I want to know exactly how you got your tentacles, and who you got them from.”

Itona raised an eyebrow in question and leaned back in his chair, crossing his arms. “I got them from Shiro, obviously.” He casually took a sip of his drink, keeping a cautious eye on Nagisa.

“But… how did you get them?” Nagisa asked, leaning forward and placing his arms on the table. He wanted to get _precise_ answers from Itona, no matter how long it took, or how stressful it was going to be.

“As you already know,” Itona started, placing his cup on the table. “He sought me out after the family business was closed down.”

“But how did he give you the tentacles? Where did he take you and what did he do?”

Itona lowered his head and put his hand on his chin, taking time to think about his answer. Nagisa waited expectantly. A small feeling of excitement was spreading throughout his body – he was _finally_ going to get the answers that would aid him in making his decision.

“Why do you need to know?” Itona challenged, fiddling with a napkin. He turned away from Nagisa, focusing all of his attention onto the napkin.

Nagisa widened his eyes. “Uh…”  
  
Sweat was gathering on his brow. He wasn’t sure if telling Itona about his master plan was the brightest idea. Then again, the plan _itself_ wasn’t the greatest idea.

Where would the harm be in telling the other boy about what he was going to do? He _was_ going to find out about it eventually, after all.

Nagisa leaned in further and lowered his voice to a hushed whisper. “I’m going to get tentacles,” he said. “It’ll be my ultimate assassination attempt.”

Itona stopped playing with the napkin and slowly turned to look at Nagisa, an eyebrow raised in question.

“You’re crazy,” he snorted. “You’re basically signing your own death warrant.”

Nagisa sighed and lowered his head. “Itona, if we don’t kill Korosensei anytime soon, the world will blow up. That’s why I’m taking this risk.”

Itona leaned forward in his chair, nearly knocking over his cup of coffee. “You can always take risks that are less riskier,” he replied, his voice calm and collected. “Believe me, Nagisa. Having tentacles is no walk in the park.”

Nagisa leaned back in his chair and sighed. _That’s it,_ he thought, shutting his eyes. _I haven’t even put the assassination plan in motion, and I’ve already failed._

“Alright,” he started, voice shaking. “In that case, I won’t go out and get myself a set of nifty tentacles. But, aside from that, I’m genuinely curious about you, Itona. What happened between you and Shiro?”

Itona regarded Nagisa with a steely gaze. Deep down, he knew that Nagisa was lying about his intentions, however at the same time, he wanted to tell others that Shiro was a monster. He wanted to warn them about how much of a manipulative bastard Shiro was.

He was hoping that his story would be enough to dissuade Nagisa from getting tentacles.

“After Shiro found me in that alleyway, he took me to a laboratory on the outskirts of Tokyo…” Itona started, looking down at his drink.

Nagisa listened attentively as Itona began to recall his story in detail, taking note of anything that could help him in his quest for tentacles.

It turned out that Shiro described Itona’s mission in detail before giving him the tentacles, ensuring that Itona was one hundred percent on board with the idea. If one were to draw an impression of Shiro from Itona’s story alone, then they’d think that Shiro was a saint. 

“Don’t get me wrong,” Itona said, after explaining the first bit of his story. “He’s still a horrible person. The way he cast me aside, after he declared that I was worthless to him…”

Nagisa nodded. He knew that Shiro was strict when it came to picking who he wanted to work with. But, he was certain that he could pull off the assassination before Shiro threw him aside; if he just combined Karasuma’s tactics with the power of his tentacles, then assassinating Koro-Sensei wouldn’t be an issue.

Him and Itona were different. Itona had no training prior to arriving at Class 3-E. Nagisa, on the other hand, was devoted to assassination training. Nagisa’s training, combined with the sheer power of the tentacles and Shiro’s tactics, would be enough to take Korosensei down.

“He’s a monster,” Itona finished, glaring at Nagisa. “He has no sympathy for anyone but himself.”

Nagisa finished off his latte and looked back up at Itona.

_I’m going to do this, no matter what it takes._

“Itona,” he started, his voice calm. “Do you mind writing the laboratory address on a clean napkin?”

Itona’s eyes widened in horror. “I’m not going to send you towards your death, Nagisa.”

“If I die or get hurt, I’ll take all the blame for myself,” Nagisa smiled, pushing a fresh napkin in Itona’s direction. “All I need you to do is to give me the address.”

Itona produced a pen from his pocket and reluctantly scrawled the laboratory address on the napkin, scowling as he wrote. He already felt the familiar sense of helplessness creeping up on him – a niggling thought at the back of his brain telling him that there was no stopping Nagisa and whatever he had in store. 

The purpose of his talk was to _warn_ Nagisa, not rile him up.

“I hope you change your mind before you enter,” he whispered, sliding the napkin back to Nagisa. “You really have no idea about what you’re getting into.”

Nagisa took a look at the address and smiled, noting that Shiro’s hideout was a mere fifteen minute walk away from his place. Getting there – and coming back – wouldn’t be an issue at all.

“Thank you,” he said, getting up from the table. He bowed in front of him and scrunched the napkin up in his palm.

“Please, keep this a secret from the rest of Class 3-E,” he said, his voice trembling. “If anyone asks you about this… well… you never told me anything.

Nagisa fished around in his pocket for a set of small bills and placed them on the table, eyeing Itona with a determined look on his face.

“For the lunch,” he explained, not peeling his gaze away from Itona’s look of shock. “You can keep the change, if you’d like.”

Nagisa turned and made his way towards the exit, his head held high. He didn't stop to properly think about what he was going to do. There were better things to do – bigger fish to fry – and having second thoughts about an assassination plan was not one of them.

He was sure that his assassination plan wouldn’t fail. It _couldn’t_ fail.

“I’ll see you at school, Itona.” Nagisa said, stopping at the door. He gave the other boy one last smile before stepping out onto the busy streets of Tokyo. 

 

***

 

A few hours later, Nagisa found himself standing outside of Shiro’s ‘laboratory’. On the outside, it looked to be a small and cramped office space – the type of facility that _wouldn’t_ be suitable for conducting tentacle-related lab work.

Nagisa double-checked the address scrawled on the napkin and the giant sign posted in front. The address that Itona had given him matched the address on the building, so he definitely wasn’t at the wrong place.

Heart pounding, Nagisa made his way towards the lobby of the office. He shoved the napkin in his pocket and pushed the front door open, expecting to see a group of businessmen strolling around the bottom floor.

He was wrong.

What greeted him was the sight of numerous scientists walking about, holding clipboards and discussing things that Nagisa couldn’t make out nor understand. All of them appeared to be too busy to deal with a simple junior high kid.

To make matters worse, the place seemed to lack a front desk. _Huh, weird. What kind of office doesn't have a front desk?_

Nagisa walked over to the center of the room, hoping to catch a glimpse of someone who looked like Shiro. However, while doing so, he walked right into a burly man with a labcoat, holding a rack of test tubes.

The impact was enough to send both people stumbling back a few steps, with the man in the labcoat coming close to dropping the tubes.

“Hey,” he called, storming over to Nagisa. “What’re you doing here, shrimp? This building is for authorized personnel only.”

Nagisa sheepishly looked down at the floor, trying his best to conceal his intense blush. “Ah, sorry, sir. I was just wondering if you knew where I-”

“Leave him to me.”

Nagisa’s eyes widened. It was near impossible to not recognize the voice, especially after interacting with its owner a few weeks ago.

_Shiro._

“He’s here for me,” Shiro said, placing a hand on Nagisa’s shoulder. Nagisa looked up at him, and saw that he was still dressed in his typical white robe – he hadn’t bothered to fit in with the rest of the building.

The other scientist was now visibly nervous, and looked as if he was about to drop the rack of test tubes. 

“Continue with your work,” Shiro said, guiding Nagisa away from the packed foyer. “We’ve got business of our own to attend to.”

Shiro led Nagisa to a nearby elevator, relieving the boy of unwanted attention. The two stepped inside a crowded elevator, causing Nagisa to timidly look down once again. Noting his discomfort, Shiro bid the others leave the elevator, making Shiro and Nagisa the only ones in the lift. 

The doors shut. Nagisa was now alone with the being that would grant him power.

Just as Nagisa was about to present his plan, Shiro spoke.

“I know what you want.”

Nagisa stared at him in awe. He hadn’t revealed his plans to anyone other than Itona _. How on Earth did Shiro know about my little plan?_ he thought, sweat forming at his brow.

Shiro regarded him. “You’re a strong one. Possibly the strongest in that class. We will have no problem in fulfilling your request.”

Nagisa gulped and slowly nodded. “I… I was told that I had potential.”

“And we’re going to make that potential grow. Follow me.”

The elevator opened to a dimly lit room, with the only furniture being a high-tech examination table attached to some machines. A small cart sat in the corner of the room, bearing syringes filled with a mysterious, murky substance.

Shiro casually made his way over to the cart and picked up a syringe, twirling it in his hand.

 _“This_ is what’s going to make you powerful. Your strength will be ten times stronger than Itona’s.”

Nagisa slowly walked towards Shiro, keeping his eyes trained on the syringe. He was drawn to it in the same way that moths were drawn to light – transfixed with the concept of overpowered strength.

“What an eager child,” Shiro chuckled. “You’re an only child, yes?”

Nagisa nodded. He turned around and brushed his hair aside, revealing the nape of his neck. His heart was thudding, and his mind was swimming with an assortment of second thoughts – but it was too late to change his mind.

“Let us become brothers in power, then.” Shiro said, raising the syringe above Nagisa’s neck. “Here’s to killing that monster of an octopus.” 

Nagisa felt the syringe pierce his skin, however, it wasn’t as painful as he’d anticipated. It felt like a regular needle was being inserted into his neck, bringing no positive or negative side effects. 

It all began once Shiro removed the needle. A strange new power was coursing through Nagisa’s veins, making him feel more energetic. He wasn’t sure about the limits of his power, but those were to be tested in the days to follow.

In a few days’ time, he’d be the most powerful in Class 3-E. He’d be the one to assassinate Korosensei in a single fell swoop, using a display of power that would even bring the likes of Karasuma-sensei to his knees.

_What do you want to be?_

The tentacles’ question was a mere whisper, however it resonated in Nagisa’s brain, the question bouncing off the walls of his mind.

However, the question brought unbearable pain. It felt like countless bugs were slowly eating away at Nagisa’s mind and tearing him apart from the inside, leaving him focused on the pain and unable to think about the question.

Nagisa doubled over and held his hands to his nape, shutting his eyes and gritting his teeth at the growing discomfort.

“It hurts, yes?” Shiro chuckled, walking up to the smaller boy. He placed a hand under Nagisa’s chin and jerked his head upwards, forcing Nagisa to look him directly in the eyes. Nagisa was hit by another wave of pain and tried to force his head down, however Shiro kept his head immobilized.

“You asked for this,” he hissed. “Now, be a good boy and answer the tentacles.” 

Nagisa forced his eyes open and focused on numbing the pain.

The tentacles asked again.

_What do you want to be?_

Tears running down his face, Nagisa opened his mouth and spoke.

“I…” he stammered, desperately trying to keep the pain at bay. “I want to be the strongest assassin in existence.”


	2. Chapter 2

**Notes for the Chapter:**

> Hey! Sorry for the long wait in between updates... a mix of schoolwork and a lack of motivation kept me from updating.
> 
> Regardless, I hope you all enjoy~! Sadly, this one's a bit short.
> 
> (also I am currently hashing out details for another AssClass fic so stay tuned for that!)

_This is no ordinary classroom,_ Korosensei mused, casually making his way down the hallway. He clutched his roll book close to his chest and chuckled, silently chastising himself for thinking such an obvious thought.

 _Of course they're not ordinary,_ he grinned, coming to a stop in front of the door to Class 3-E. He placed a single tentacle on to the door and started to slide it open at the slowest of paces.  _They were taught by me, after all. Ordinary is simply something that we all_ can't  _do._

Korosensei slid the door open and slithered into the classroom, expecting to see his twenty-eight students chattering away about assassination tactics and various lesson plans. Satisfied with his expectation, Korosensei smiled to himself, quickly doing a mental review of his (very disorganized) lesson plan.

The yellow octopus made his way to the front of the class, mumbling incoherent thoughts about how today's lessons were going to pan out. Oblivious to his surroundings, he calmly placed his roll book on his desk and took a deep breath.

Then he looked up.

"Whaaaa-?!"

The entire class seemed unfazed by the creature's arrival. Contrary to Korosensei's hopes and beliefs, the class was standing still, an air of tranquility about them. What shocked him most, however, was the fact that they were all brandishing assault rifles – guns that were designed to be harmless to the average human, but lethal to him.

_Anti-Sensei BBs. What else would they use as ammunition?_

"Mornin', teach," Karma greeted, casually fiddling with his gun. He gave off a sly smile and winked, cocking his gun in Korosensei's general direction. "Hope your senses aren't too dull this morning. It'd be a shame if we got this over with in under a minute."

Karma fired a single warning shot, the BB bouncing off the blackboard and landing on the floor with a quiet  _tap._ The rest of the class, who opted not to make a move upon the fired shot, was transfixed on Karma's gun - its barrel still pointed at Korosensei.

Korosensei chuckled, his face lighting up with green stripes. He set his roll book on his desk and took the time to set his students in a passable assassination stance, moving their arms and guns so that they all faced the front.

"You can't possibly expect to assassinate me when your weapons are facing the ground," he said, quickly materializing at the front of the class. He raised a tentacle and chuckled once again. "Now, the positions that you've assumed are much more ideal for an assassination attempt, right?"

The class remained silent, however Korosensei knew that they each student was put in an optimal position. The entire front of the classroom was within range of each student's crosshair. Korosensei had nowhere to hide - but he had  _everywhere_ to run.

He gave the students one last inspection, reflecting on how much they've grown over the past year. When he first came to the class, he saw a bunch of innocent faces - people that tended to balk at the first sense of danger. Over time, he took their innocence and corrupted it, replacing all soft feelings with courage and an underlying desire to kill supernatural monsters.

Now, they had evolved. They had become full-fledged killers, ready to assassinate whenever the situation called for it.

 _But, are they skilled enough to assassinate_ me? Korosensei thought. He gave one final chuckle, picking up his roll book and slowly opening it.

The action was enough to send the class into a frenzy, the once-silent class coming to life with the sound of rapid gunfire. Countless anti-Sensei BBs bounced off the blackboard, all of them failing to find their mark, as Korosensei zipped from one end of the classroom to another, laughing as he went.

"That  _goddamn_ sonofabitch," Karma muttered, gritting his teeth. He took his finger off of the trigger, and held up a hand, looking up to bark an order at his classmates.

"Forget the original plan," he yelled, jerking his gun in another direction. "Change the firing plan to plan B!"

Instead of keeping their guns aimed in one certain position, the class decided to move their guns in a multitude of directions, praying that they didn't accidentally injure a fellow classmate in the process. While the firing trajectory became a lot less predictable, Korosensei dodged the bullets, using even less effort than before.

"Karma!" Korosensei called, still zooming from position to position. He'd even decided to break free from the restraints of the front of the class, choosing to materialize at virtually any location in the classroom.

Karma scowled and grit his teeth, attempting to follow Korosensei's trail. "I'm here, Teach. Don't worry about it." His voice, competing with the sound of other firing guns, was barely audible.

“In that case, I _won't_ worry.” Korosensei responded. “Now, moving on. Isogai?”  
  
“Right here, sir!"  
  
“Okaijima?”

“Here!”

The roll call continued in this manner, with the class continuing their assassination efforts, and with Korosensei shouting student names over the sound of gunfire. Judging by how well roll call was going, every student seemed to be present. 

“Nagisa!”

There was no response - not even the faintest of voices could be heard over the sound of gunfire.

“Nagisa, I need you to speak up, please! It’s hard to hear you over the noise!"

The class, intruiged by the absence of their colleague, quickly stopped firing, letting the last of the fired BBs clatter down to the floor. Confused, they looked around the classroom, conjuring thoughts on why he  _wouldn't_ be here.

The only person who didn't join in on the discussion was Itona, who had suddenly found his desk much more intriguing than the class' dilemma. Memories of yesterday's lunch with Nagisa came rushing back to his mind – his request, his seriousness, and most unsettling – the smile he had given him before he left the restaurant.

Itona's stomach dropped, his mind suddenly assaulted with a fury of undesirable scenarios.  _What if Nagisa experienced the hellish symptoms right after he got his tentacles? What if he's... he's..._

"Itona?"

Itona's trancelike state was was broken by the voice of Kayano, who had quietly approached him amidst all of the chaos. Like everyone else, she looked visibly worried.

Itona turned towards Kayano, trying his best to conceal the guilt that was written all over his face.

"Yes, Kayano?" he asked, peering at her with big, curious eyes.

Kayano took a seat in an adjacent desk. "You've been awfully quiet. Do you know anything about Nagisa's absence?"

"He's probably sick or something. I wouldn't give it too much thought." he replied, dismissive of the question. Itona shrugged and looked back down at his desk, hoping that Kayano would leave him alone to brood.

However, fate had other ideas, despite Itona's reluctance to speak about the situation.

As if responding to Kayano's question, the blurry image of a blue tentacle burst through the classroom's door, darting out and reaching across the front of the classroom.


End file.
